The present invention relates to a hydraulic brake actuation device for motor vehicles equipped with an antiskid system which includes a continuous-delivery pressure medium source supplying a first pressure medium circuit, influenceable by a pedal-operated control device, and of a first master cylinder which, via a valve arrangement, is connected to the first pressure medium circuit and to a first brake circuit which is independent of the first pressure medium circuit, the master cylinder's piston being operable by the pressure in the first pressure medium circuit and/or by the brake pedal.
Such a hydraulic brake actuation device has come to knowledge in the German Pat. No. DE-AS 20 17 185. It includes a housing for the accomodation of the control device and of a master brake cylinder connected to the housing. A piston divides the control device into two pressure chambers, a third chamber being defined by a recess around the circumference of the piston. The first pressure chamber supplied by the pressure medium source serves an an inlet chamber and is penetrated by a pedal-operated valve tappet opposite which a bore is coaxially arranged in the piston, said bore connecting the inlet chamber with the third chamber, which is the outlet chamber. The second chamber communicates with the compensation reservoir and is filled with pressure medium, only. It is penetrated by a tappet which is sealingly led from the control housing into the master brake cylinder and which thus mechanically connects the piston with the master brake cylinder piston. The master brake cylinder's pressure chamber penetrated by the tappet communicates with the inlet chamber of the control housing by means of a valve arrangement. The brake circuit pertaining to the master brake cylinder communicates with the wheel brake cylinders of the front axle. The pressure medium source constantly delivers to the inlet chamber and, through the bore in the piston into the outlet chamber, back into the storage tank which simultaneously serves as compensation reservoir. If, due to the actuation of the pedal, the valve tappet tries to close the bore in the piston, in the inlet chamber a pressure will build up which, via the valve arrangement, will act on the master brake cylinder piston and displace the latter, thus building up a pressure in the brake circuit of the master brake cylinder. A valve arrangement directly connects the rear axle with the pressure medium circuit. Thus, it is safeguarded that the braking pressure will be controllable in the brake circuit of the front axle without any fluid losses. With respect to antiskid systems, however, it has proved disadvantageous that this system will allow a joint control of the front wheels, only. In order to achieve an optimum short braking distance as well as to safeguard the steerability of the vehicle what is aimed at is a serarate control of the front wheels.